NeXTSTEP is a discontinued object-oriented, multitasking operating system based on UNIX. It was developed by NeXT Computer in the late 1980s and early 1990s and was initially used for its range of proprietary workstation computers such as the NeXTcube. It was later ported to several other computer architectures.
Although relatively unsuccessful at the time, it attracted interest from computer scientists and researchers. It was used as the original platform for the development of the Electronic AppWrapper, the first commercial electronic software distribution catalog to collectively manage encryption and provide digital rights for application software and digital media, a forerunner of the modern "app store" concept. It was also the platform on which Tim Berners-Lee created the first web browser, and on which id Software developed the video game 
Doom.... More Info »
After the purchase of NeXT by Apple, it became the source of the popular operating systems 
macOS, 
iOS, watchOS, tvOS, and audioOS. Many bundled macOS applications, such as 
TextEdit, 
Apple Mail, and Chess, are descendants of NeXTSTEP applications.
